Spread-spectrum changeable base station

ABSTRACT

A base subunit receives a signal over a first frequency. A plurality of despread voice signals are produced using the received signal. The despread signals and a voice signal generated at the base subunit are combined. The combined signal is mixed with a chipping sequence. The mixed combined signal is transmitted at a second frequency.

[0001] This application is a continuation of U.S. patent application No.09/878,647, filed on Jun. 11, 2001, which is a continuation of U.S.patent application No. 09/133,047, filed Aug. 13, 1998, now U.S. Pat.No. 6,295,388, which is a continuation of U.S. patent application No.08/814,809, filed Mar. 10, 1997, now U.S. Pat. No. 5,926,465, which is acontinuation of U.S. patent application No. 08/268,186, filed Jun. 29,1994, now U.S. Pat. No. 5,610,906.

BACKGROUND

[0002] This invention relates to spread-spectrum communications, andmore particularly, to a method and system for handing off a base stationamong a plurality of users in a spread-spectrum network.

[0003] Spread-spectrum modulation is a well developed art, in terms ofgenerating chipping sequences, and spread-spectrum processing datasignals with the chipping sequences. Using this technology,communication links may be established among a transmitter and areceiver in remote locations. Also, networks may be established, using aconference calling spread-spectrum technique. Conference callingspread-spectrum techniques are disclosed in U.S. Pat. No. 5,179,572entitled SPREAD SPECTRUM CONFERENCE CALLING SYSTEM AND METHOD, toSchilling, and in U.S. Pat. No. 5,263,045, entitled SPREAD SPECTRUMCONFERENCE CALL SYSTEM AND METHOD, to Schilling.

[0004] A problem may exist where a spread-spectrum conference callingsystem is set up, but the base station may need to change hands. Forexample, in a military environment, a platoon may use spread-spectrummodulation for conference calling among the members of the platoon. Aparticular unit in the platoon may be designated as the base station.The cited prior art does not teach how to change a base station from oneplatoon to another or what would happen among units in the platoon inthe event it became necessary to effectuate such a change.

SUMMARY

[0005] A base subunit receives a signal over a first frequency. Aplurality of despread voice signals are produced using the receivedsignal. The despread signals and a voice signal generated at the basesubunit are combined. The combined signal is mixed with a chippingsequence. The mixed combined signal is transmitted at a secondfrequency.

BRIEF DESCRIPTION OF THE DRAWING(S)

[0006] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate preferred embodimentsof the invention, and together with the description serve to explain theprinciples of the invention.

[0007]FIG. 1A is a block diagram of a base subunit using a plurality ofmixers;

[0008]FIG. 1B is a block diagram of a base subunit using a plurality ofmatched filters;

[0009]FIG. 2A is a block diagram of a remote subunit using a mixer;

[0010]FIG. 2B is a block diagram of a remote subunit using a matchedfilter; and

[0011]FIG. 3 is a block diagram of a command subunit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0012] Reference now is made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings, wherein like reference numerals indicate likeelements throughout the several views.

[0013] The present invention provides a unique solution to the problemof a plurality of spread spectrum units in use in a mobile environmentin which any one of the spread-spectrum units is vulnerable toneutralization while maintaining communication between all thespread-spectrum units remains crucial. The spread-spectrum changeablebase station finds application in a platoon of units, in an armyenvironment, or in a law enforcement application, where a transportablebase station might be set up for controlling a plurality of spreadspectrum remote units. The problem being addressed for each of theseapplications is what happens when the base unit becomes disabled ornonfunctional. In the military environment, the base station may bedestroyed. In a law enforcement situation, the mobility of the pluralityof spread-spectrum units may have a requirement that the base stationchange from one unit to another.

[0014] The spread-spectrum system has a plurality of spread-spectrumunits, with each spread-spectrum unit having a base subunit, a remotesubunit, and a command subunit. The use of the term “subunits” fordesignating the base subunit, remote subunit, and command subunit, isfor purposes of illustrating the invention. The invention may be builtas one totally integrated unit, or as a mixture of more than one unit.

[0015] The base subunit is illustratively shown in FIGS. 1A and 1B. Thebase subunit includes receiving means, despreading means, demodulatingmeans, combining means, converting means, spread-spectrum processingmeans, and transmitting means. The despreading means is coupled betweenthe receiving means and the demodulating means. The combining means iscoupled to the demodulating means and the converting means. Thespread-spectrum processing means is coupled to the converting means andthe transmitting means.

[0016] The receiving means is shown in FIG. 1A as antenna 11 coupled toradio frequency/intermediate frequency (RF/IF) amplifier and filtersection 12. The despreading means is illustrated as a plurality ofmixers 13, 14, 15. As shown in FIG. 1B, the despreading means may alsobe embodied as a plurality of matched filters 22, 23, 24. Each of theplurality of mixers 13, 14, 15 has a chipping-sequence g₁ (t), g₂ (t), .. . , g_(N) (t), respectively, for mixing with the receivedspread-spectrum signal. The plurality of chipping sequences is matchedto the chipping sequence of the desired spread-spectrum signal to bedespread.

[0017] The demodulating means and combining means is shown as thedemodulator 16 and combiners 17A, 17B. Combiners 17A, 17B may be asingle combiner performing the combining function, or separatecombiners. The converting means is shown as an analog-to-digitalconverter 18. The spread-spectrum processing means is illustrated asproduct device 19, having a chipping sequence for spreading the datasignal from analog-to-digital converter 18. The transmitting means isillustrated as transmitter 20 and antenna 21.

[0018] The RF/IF amplifier and filter circuits 12 are coupled to theantenna 11 and to the plurality of mixers 13, 14, 15. The plurality ofmixers 13, 14, 15 is coupled to the demodulator 16 and combiner 17A,17B. The analog-to-digital converter 18 is coupled to the combiner 17Band to the product device 19. The transmitter 20 is coupled to theproduct device 19 and to antenna 21. Antenna 21 and antenna 11 may bethe same antenna with the appropriate isolation circuits, or differentantennas. The RF/IF amplifier and filter circuits 12 receive at a firstfrequency, f₁, a plurality of spread-spectrum signals transmitted fromthe plurality of spread-spectrum units. The plurality of spread-spectrumsignals are despread by the plurality of mixers 13, 14, 15. As shown inFIG. 1B, the despreading means may also be embodied as a plurality ofmatched filters 22, 23, 24. The output of the plurality of mixers 13,14, 15 is a plurality of despread-spread-spectrum signals. Thedemodulator 16 demodulates the plurality of despread-spread-spectrumsignals to generate a plurality of demodulated signals. The combiner 17Acombines the plurality of demodulated signals. The combined plurality ofdemodulated signals and a local signal from the base station may becombined by second combiner 17B to generate a combined signal. The term“combined signal”, as used herein, is an analog signal including thevoice of the base station and the combined demodulated signals of thecombiners 17A, 17B.

[0019] The combined signal is converted to a base-data signal byanalog-to-digital converter 18. The term “base-data signal,” as usedherein, is the digital signal coming from the analog-to-digitalconverter 18, and includes the converted analog signals and the datasignal at the base station.

[0020] The product device 19 spread-spectrum processes the base-datasignal from analog-to-digital converter 18, with a base-chippingsequence. The spread-spectrum-processed-base-data signal is transmittedas a base-spread-spectrum signal by transmitter 20 at the secondfrequency f₂. Antenna 11 and antenna 21 may be a single antenna, servingboth the receiver and transmitter.

[0021] The remote subunit is illustrated in FIGS. 2A and 2B and includesa receiver portion, a transmitter portion, receiving means, despreadingmeans, and demodulating means. The transmitting portion includesconverting means, spread-spectrum processing means and transmittingmeans. The receiving means receives at the second frequency thebase-spread-spectrum signal. The despreading means despreads thebase-spread-spectrum signal as a despread-base-spread-spectrum signal.The demodulating means demodulates the despread-base-spread-spectrumsignal as a base-analog signal.

[0022] The converting means converts a remote-analog signal to aremote-data signal. The remote-analog signal typically is the voice ofthe remote station. The base-analog signal typically is the plurality ofvoice signals from the base station. The spread-spectrum processingmeans processes the remote-data signal with a remote-chipping sequence.The transmitting means transmits at the first frequency thespread-spectrum-processed-remote-data signal as one of the plurality ofspread-spectrum signals, which are received at the base subunit.

[0023] As shown in FIG. 2A, the receiving means includes an antenna 31and RF/IF amplifier and filter circuitry 32. The despreading means anddemodulating means are embodied as mixer 33 and demodulator 34,respectively. As shown in FIG. 2B, the despreading means may also beembodied as a matched filter 39. The RF/IF amplifier and circuitry 32 iscoupled between antenna 31 and the mixer 33. The demodulator 34 iscoupled to the mixer 33.

[0024] The base-spread-spectrum signal at antenna 31 is amplified andfiltered by RF/IF. The base-spread-spectrum signal is despread by thebase-chipping sequence by mixer 33 to generate thedespread-base-spread-spectrum signal. The demodulator 34 demodulates thedespread-base-spread-spectrum signal as a base-analog signal. The outputof the demodulator 34 is the plurality of voice signals from the basestation.

[0025] The transmitter section of the remote subunit may have theconverting means embodied as analog-to-digital converter 35, thespread-spectrum processing means embodied as product device 36 and thetransmitting means embodied as transmitter 37 coupled to antenna 38. Theproduct device 36 is coupled between the analog-to-digital converter 35and the transmitter 37.

[0026] The analog-to-digital converter 35 converts the voice of theremote signal, designated here as the remote-analog signal, to aremote-data signal. The remote-data signal is spread-spectrum processedby the product device 36 using remote-chipping sequence. The output ofthe product device 36 is the spread-spectrum-processed-remote-datasignal. The transmitter 37 transmits thespread-spectrum-processed-remote-data signal using antenna 38, as one ofthe plurality of spread-spectrum signals. Antenna 31 and antenna 38 maybe combined as a single antenna serving both functions.

[0027] The command subunit is illustrated in FIG. 3. The command subunitincludes initiating means, broadcasting means, and receiving means. Theinitiating means initiates a command signal, upon activation by thelocal user of that spread-spectrum unit. The command signal activatesthe base subunit in that spread-spectrum unit. The broadcasting meansbroadcasts the command signal to the plurality of spread-spectrum units.The receiving means receives the command signal when broadcast from adifferent spread-spectrum unit. The activating means activates theremote subunit upon receiving the command signal.

[0028] The initiating means is illustrated in FIG. 3 as a push buttonswitch 43. The broadcasting means is illustrated as a transmitterportion of the transmitter/receiver 42. The transmitter transmits atfrequency f₃. The receiving means is illustrated as the receiver portionof transmitter/receiver 42. The receiver receives at frequency f₃. Thetransmitter/receiver 42 is coupled to antenna 41 for radiating andreceiving signals. The activating means includes the necessary circuitryfor disconnecting the base subunit and activating the remote subunit ofa particular spread-spectrum unit. The activating means is illustratedas control circuitry 44. The present invention may also be used for datain place of voice signals.

[0029] In use, a particular spread-spectrum unit might be operating withits remote subunit activated. Thus, the remote subunit of thatparticular spread-spectrum unit receives at the second frequency thebase-spread-spectrum signal, and despreads the base-spread-spectrumsignal as a despread-base-spread-spectrum signal. Thedespread-base-spread-spectrum signal is demodulated. Thus, thatparticular spread-spectrum unit receives all of the base signals via itsremote subunit. While transmitting to the plurality of spread-spectrumunits, that particular spread-spectrum unit converts the voice signal,embodied as the remote-analog signal, to the remote-data signal. Theremote-data signal is spread-spectrum processed and transmitted at thefirst frequency as one of the plurality of spread-spectrum signals.

[0030] Upon initiation of the command signal by the user of thatparticular spread-spectrum unit, by pushing push button 43, thatparticular spread-spectrum unit switches from operating with the remotesubunit to operating with the base subunit. At the same time, thecommand signal is radiated to the other spread-spectrum units of theplurality of spread-spectrum units. Upon receiving the command signal,each of the spread-spectrum units has its remote subunit activated andthereafter works in a remote subunit mode. The particularspread-spectrum unit has then become the base station.

[0031] When operating as the base station, the particularspread-spectrum unit has its base subunit activated. Accordingly, theplurality of spread-spectrum signals transmitted from the plurality ofspread-spectrum units at each unit, is received by the RF/IF amplifierand circuitry 12 via antenna 11. The plurality of spread-spectrumsignals are despread by the plurality of mixers 13, 14, 15, anddemodulated by the demodulator 16 which outputs a demodulated signal.The plurality of demodulated signals from combiner 17A are the voicesfrom the plurality of remote stations. The voices from the plurality ofremote stations are combined with the voice of the base station bycombiner 17B, and converted by analog-to-digital converter 18 to thebase-data signal. The base-data signal is spread-spectrum processed bythe product device 19 and transmitted by transmitter 20 and via antenna21 at the second frequency.

[0032] It will be apparent to those skilled in the art that variousmodifications can be made to the spread-spectrum changeable base stationof the instant invention without departing from the scope or spirit ofthe invention, and it is intended that the present invention covermodifications and variations of the spread-spectrum changeable basestation provided they come within the scope of the appended claims andtheir equivalents.

What is claimed is:
 1. A base subunit for use in a wireless spreadspectrum communication system comprising: an antenna for receiving asignal over a first frequency; a plurality of mixers for mixing thereceived signal with a plurality of chipping sequences to produce aplurality of despread voice signals; a combiner combining the despreadsignals and a voice signal generated at the base subunit; a productdevice for mixing the combined signal with a chipping sequence; and anantenna for transmitting the mixed combined signal at a secondfrequency.
 2. The base subunit of claim 1 further comprising ademodulator for demodulating the despread voice signals prior to thecombining.
 3. The base subunit of claim 1 wherein the combiner comprisesa first and second combiner, the first combiner combines the despreadsignals and the second combiner combining the combined despread signalswith the voice signal generated at the base subunit.
 4. The base subunitof claim 1 further comprising an analog to digital converter forconverting the combined signal into a digital signal.
 5. The basesubunit of claim 3 wherein the output of the first combiner is acombined voice signal of a plurality of remote units.
 6. A base subunitfor use in a wireless spread spectrum communication system comprising:an antenna for receiving a signal over a first frequency; a plurality ofmatched filters for mixing the received signal to produce a plurality ofdespread voice signals; a combiner combining the despread signals and avoice signal generated at the base subunit; a product device for mixingthe combined signal with a chipping sequence; and an antenna fortransmitting the mixed combined signal at a second frequency.
 7. Thebase subunit of claim 6 further comprising a demodulator fordemodulating the despread voice signals prior to the combining.
 8. Thebase subunit of claim 6 wherein the combiner comprises a first andsecond combiner, the first combiner combines the despread signals andthe second combiner combining the combined despread signal with thevoice signal generated at the base subunit.
 9. The base subunit of claim5 further comprising an analog to digital converter for converting thecombined signal into a digital signal.
 10. The base subunit of claim 8wherein the output of the first combiner is a combined voice signal of aplurality of remote units.
 11. A base subunit for use in a wirelessspread spectrum communication system comprising: means for receiving asignal over a first frequency; means for producing a plurality ofdespread voice signals using the received signal; means for combiningthe despread signals and a voice signal generated at the base subunit;means for mixing the combined signal with a chipping sequence; and meansfor transmitting the mixed combined signal at a second frequency. 12.The base subunit of claim 11 wherein the producing means is a pluralityof mixers.
 13. The base subunit of claim 11 wherein the producing meansis a plurality of matched filters.
 14. The base subunit of claim 11comprising a demodulator for demodulating the despread voice signalsprior to the combining.
 15. The base subunit of claim 11 wherein thecombining means comprises a first and second combiner, the firstcombiner combines the despread signals and the second combiner combiningthe combined despread signals with the voice signal generated at thebase subunit.
 16. The base subunit of claim 11 further comprising ananalog to digital converter for converting the combined signal into adigital signal.
 17. The base subunit of claim 15 wherein the output ofthe first combiner is a combined voice signal of a plurality of remoteunits.